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open.c

/*
 *  linux/fs/open.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/string.h>
#include <linux/mm.h>
#include <linux/file.h>
#include <linux/quotaops.h>
#include <linux/fsnotify.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <linux/fcntl.h>
#include <asm/uaccess.h>
#include <linux/fs.h>
#include <linux/personality.h>
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/rcupdate.h>
#include <linux/audit.h>
#include <linux/falloc.h>

int vfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
      int retval = -ENODEV;

      if (dentry) {
            retval = -ENOSYS;
            if (dentry->d_sb->s_op->statfs) {
                  memset(buf, 0, sizeof(*buf));
                  retval = security_sb_statfs(dentry);
                  if (retval)
                        return retval;
                  retval = dentry->d_sb->s_op->statfs(dentry, buf);
                  if (retval == 0 && buf->f_frsize == 0)
                        buf->f_frsize = buf->f_bsize;
            }
      }
      return retval;
}

EXPORT_SYMBOL(vfs_statfs);

static int vfs_statfs_native(struct dentry *dentry, struct statfs *buf)
{
      struct kstatfs st;
      int retval;

      retval = vfs_statfs(dentry, &st);
      if (retval)
            return retval;

      if (sizeof(*buf) == sizeof(st))
            memcpy(buf, &st, sizeof(st));
      else {
            if (sizeof buf->f_blocks == 4) {
                  if ((st.f_blocks | st.f_bfree | st.f_bavail) &
                      0xffffffff00000000ULL)
                        return -EOVERFLOW;
                  /*
                   * f_files and f_ffree may be -1; it's okay to stuff
                   * that into 32 bits
                   */
                  if (st.f_files != -1 &&
                      (st.f_files & 0xffffffff00000000ULL))
                        return -EOVERFLOW;
                  if (st.f_ffree != -1 &&
                      (st.f_ffree & 0xffffffff00000000ULL))
                        return -EOVERFLOW;
            }

            buf->f_type = st.f_type;
            buf->f_bsize = st.f_bsize;
            buf->f_blocks = st.f_blocks;
            buf->f_bfree = st.f_bfree;
            buf->f_bavail = st.f_bavail;
            buf->f_files = st.f_files;
            buf->f_ffree = st.f_ffree;
            buf->f_fsid = st.f_fsid;
            buf->f_namelen = st.f_namelen;
            buf->f_frsize = st.f_frsize;
            memset(buf->f_spare, 0, sizeof(buf->f_spare));
      }
      return 0;
}

static int vfs_statfs64(struct dentry *dentry, struct statfs64 *buf)
{
      struct kstatfs st;
      int retval;

      retval = vfs_statfs(dentry, &st);
      if (retval)
            return retval;

      if (sizeof(*buf) == sizeof(st))
            memcpy(buf, &st, sizeof(st));
      else {
            buf->f_type = st.f_type;
            buf->f_bsize = st.f_bsize;
            buf->f_blocks = st.f_blocks;
            buf->f_bfree = st.f_bfree;
            buf->f_bavail = st.f_bavail;
            buf->f_files = st.f_files;
            buf->f_ffree = st.f_ffree;
            buf->f_fsid = st.f_fsid;
            buf->f_namelen = st.f_namelen;
            buf->f_frsize = st.f_frsize;
            memset(buf->f_spare, 0, sizeof(buf->f_spare));
      }
      return 0;
}

asmlinkage long sys_statfs(const char __user * path, struct statfs __user * buf)
{
      struct nameidata nd;
      int error;

      error = user_path_walk(path, &nd);
      if (!error) {
            struct statfs tmp;
            error = vfs_statfs_native(nd.dentry, &tmp);
            if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
                  error = -EFAULT;
            path_release(&nd);
      }
      return error;
}


asmlinkage long sys_statfs64(const char __user *path, size_t sz, struct statfs64 __user *buf)
{
      struct nameidata nd;
      long error;

      if (sz != sizeof(*buf))
            return -EINVAL;
      error = user_path_walk(path, &nd);
      if (!error) {
            struct statfs64 tmp;
            error = vfs_statfs64(nd.dentry, &tmp);
            if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
                  error = -EFAULT;
            path_release(&nd);
      }
      return error;
}


asmlinkage long sys_fstatfs(unsigned int fd, struct statfs __user * buf)
{
      struct file * file;
      struct statfs tmp;
      int error;

      error = -EBADF;
      file = fget(fd);
      if (!file)
            goto out;
      error = vfs_statfs_native(file->f_path.dentry, &tmp);
      if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
            error = -EFAULT;
      fput(file);
out:
      return error;
}

asmlinkage long sys_fstatfs64(unsigned int fd, size_t sz, struct statfs64 __user *buf)
{
      struct file * file;
      struct statfs64 tmp;
      int error;

      if (sz != sizeof(*buf))
            return -EINVAL;

      error = -EBADF;
      file = fget(fd);
      if (!file)
            goto out;
      error = vfs_statfs64(file->f_path.dentry, &tmp);
      if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
            error = -EFAULT;
      fput(file);
out:
      return error;
}

int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
      struct file *filp)
{
      int err;
      struct iattr newattrs;

      /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
      if (length < 0)
            return -EINVAL;

      newattrs.ia_size = length;
      newattrs.ia_valid = ATTR_SIZE | time_attrs;
      if (filp) {
            newattrs.ia_file = filp;
            newattrs.ia_valid |= ATTR_FILE;
      }

      /* Remove suid/sgid on truncate too */
      newattrs.ia_valid |= should_remove_suid(dentry);

      mutex_lock(&dentry->d_inode->i_mutex);
      err = notify_change(dentry, &newattrs);
      mutex_unlock(&dentry->d_inode->i_mutex);
      return err;
}

static long do_sys_truncate(const char __user * path, loff_t length)
{
      struct nameidata nd;
      struct inode * inode;
      int error;

      error = -EINVAL;
      if (length < 0)   /* sorry, but loff_t says... */
            goto out;

      error = user_path_walk(path, &nd);
      if (error)
            goto out;
      inode = nd.dentry->d_inode;

      /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
      error = -EISDIR;
      if (S_ISDIR(inode->i_mode))
            goto dput_and_out;

      error = -EINVAL;
      if (!S_ISREG(inode->i_mode))
            goto dput_and_out;

      error = vfs_permission(&nd, MAY_WRITE);
      if (error)
            goto dput_and_out;

      error = -EROFS;
      if (IS_RDONLY(inode))
            goto dput_and_out;

      error = -EPERM;
      if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
            goto dput_and_out;

      error = get_write_access(inode);
      if (error)
            goto dput_and_out;

      /*
       * Make sure that there are no leases.  get_write_access() protects
       * against the truncate racing with a lease-granting setlease().
       */
      error = break_lease(inode, FMODE_WRITE);
      if (error)
            goto put_write_and_out;

      error = locks_verify_truncate(inode, NULL, length);
      if (!error) {
            DQUOT_INIT(inode);
            error = do_truncate(nd.dentry, length, 0, NULL);
      }

put_write_and_out:
      put_write_access(inode);
dput_and_out:
      path_release(&nd);
out:
      return error;
}

asmlinkage long sys_truncate(const char __user * path, unsigned long length)
{
      /* on 32-bit boxen it will cut the range 2^31--2^32-1 off */
      return do_sys_truncate(path, (long)length);
}

static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
{
      struct inode * inode;
      struct dentry *dentry;
      struct file * file;
      int error;

      error = -EINVAL;
      if (length < 0)
            goto out;
      error = -EBADF;
      file = fget(fd);
      if (!file)
            goto out;

      /* explicitly opened as large or we are on 64-bit box */
      if (file->f_flags & O_LARGEFILE)
            small = 0;

      dentry = file->f_path.dentry;
      inode = dentry->d_inode;
      error = -EINVAL;
      if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
            goto out_putf;

      error = -EINVAL;
      /* Cannot ftruncate over 2^31 bytes without large file support */
      if (small && length > MAX_NON_LFS)
            goto out_putf;

      error = -EPERM;
      if (IS_APPEND(inode))
            goto out_putf;

      error = locks_verify_truncate(inode, file, length);
      if (!error)
            error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
out_putf:
      fput(file);
out:
      return error;
}

asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length)
{
      long ret = do_sys_ftruncate(fd, length, 1);
      /* avoid REGPARM breakage on x86: */
      prevent_tail_call(ret);
      return ret;
}

/* LFS versions of truncate are only needed on 32 bit machines */
#if BITS_PER_LONG == 32
asmlinkage long sys_truncate64(const char __user * path, loff_t length)
{
      return do_sys_truncate(path, length);
}

asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length)
{
      long ret = do_sys_ftruncate(fd, length, 0);
      /* avoid REGPARM breakage on x86: */
      prevent_tail_call(ret);
      return ret;
}
#endif

asmlinkage long sys_fallocate(int fd, int mode, loff_t offset, loff_t len)
{
      struct file *file;
      struct inode *inode;
      long ret = -EINVAL;

      if (offset < 0 || len <= 0)
            goto out;

      /* Return error if mode is not supported */
      ret = -EOPNOTSUPP;
      if (mode && !(mode & FALLOC_FL_KEEP_SIZE))
            goto out;

      ret = -EBADF;
      file = fget(fd);
      if (!file)
            goto out;
      if (!(file->f_mode & FMODE_WRITE))
            goto out_fput;
      /*
       * Revalidate the write permissions, in case security policy has
       * changed since the files were opened.
       */
      ret = security_file_permission(file, MAY_WRITE);
      if (ret)
            goto out_fput;

      inode = file->f_path.dentry->d_inode;

      ret = -ESPIPE;
      if (S_ISFIFO(inode->i_mode))
            goto out_fput;

      ret = -ENODEV;
      /*
       * Let individual file system decide if it supports preallocation
       * for directories or not.
       */
      if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
            goto out_fput;

      ret = -EFBIG;
      /* Check for wrap through zero too */
      if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
            goto out_fput;

      if (inode->i_op && inode->i_op->fallocate)
            ret = inode->i_op->fallocate(inode, mode, offset, len);
      else
            ret = -EOPNOTSUPP;

out_fput:
      fput(file);
out:
      return ret;
}

/*
 * access() needs to use the real uid/gid, not the effective uid/gid.
 * We do this by temporarily clearing all FS-related capabilities and
 * switching the fsuid/fsgid around to the real ones.
 */
asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode)
{
      struct nameidata nd;
      int old_fsuid, old_fsgid;
      kernel_cap_t old_cap;
      int res;

      if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
            return -EINVAL;

      old_fsuid = current->fsuid;
      old_fsgid = current->fsgid;
      old_cap = current->cap_effective;

      current->fsuid = current->uid;
      current->fsgid = current->gid;

      /*
       * Clear the capabilities if we switch to a non-root user
       *
       * FIXME: There is a race here against sys_capset.  The
       * capabilities can change yet we will restore the old
       * value below.  We should hold task_capabilities_lock,
       * but we cannot because user_path_walk can sleep.
       */
      if (current->uid)
            cap_clear(current->cap_effective);
      else
            current->cap_effective = current->cap_permitted;

      res = __user_walk_fd(dfd, filename, LOOKUP_FOLLOW|LOOKUP_ACCESS, &nd);
      if (res)
            goto out;

      res = vfs_permission(&nd, mode);
      /* SuS v2 requires we report a read only fs too */
      if(res || !(mode & S_IWOTH) ||
         special_file(nd.dentry->d_inode->i_mode))
            goto out_path_release;

      if(IS_RDONLY(nd.dentry->d_inode))
            res = -EROFS;

out_path_release:
      path_release(&nd);
out:
      current->fsuid = old_fsuid;
      current->fsgid = old_fsgid;
      current->cap_effective = old_cap;

      return res;
}

asmlinkage long sys_access(const char __user *filename, int mode)
{
      return sys_faccessat(AT_FDCWD, filename, mode);
}

asmlinkage long sys_chdir(const char __user * filename)
{
      struct nameidata nd;
      int error;

      error = __user_walk(filename,
                      LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_CHDIR, &nd);
      if (error)
            goto out;

      error = vfs_permission(&nd, MAY_EXEC);
      if (error)
            goto dput_and_out;

      set_fs_pwd(current->fs, nd.mnt, nd.dentry);

dput_and_out:
      path_release(&nd);
out:
      return error;
}

asmlinkage long sys_fchdir(unsigned int fd)
{
      struct file *file;
      struct dentry *dentry;
      struct inode *inode;
      struct vfsmount *mnt;
      int error;

      error = -EBADF;
      file = fget(fd);
      if (!file)
            goto out;

      dentry = file->f_path.dentry;
      mnt = file->f_path.mnt;
      inode = dentry->d_inode;

      error = -ENOTDIR;
      if (!S_ISDIR(inode->i_mode))
            goto out_putf;

      error = file_permission(file, MAY_EXEC);
      if (!error)
            set_fs_pwd(current->fs, mnt, dentry);
out_putf:
      fput(file);
out:
      return error;
}

asmlinkage long sys_chroot(const char __user * filename)
{
      struct nameidata nd;
      int error;

      error = __user_walk(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY | LOOKUP_NOALT, &nd);
      if (error)
            goto out;

      error = vfs_permission(&nd, MAY_EXEC);
      if (error)
            goto dput_and_out;

      error = -EPERM;
      if (!capable(CAP_SYS_CHROOT))
            goto dput_and_out;

      set_fs_root(current->fs, nd.mnt, nd.dentry);
      set_fs_altroot();
      error = 0;
dput_and_out:
      path_release(&nd);
out:
      return error;
}

asmlinkage long sys_fchmod(unsigned int fd, mode_t mode)
{
      struct inode * inode;
      struct dentry * dentry;
      struct file * file;
      int err = -EBADF;
      struct iattr newattrs;

      file = fget(fd);
      if (!file)
            goto out;

      dentry = file->f_path.dentry;
      inode = dentry->d_inode;

      audit_inode(NULL, dentry);

      err = -EROFS;
      if (IS_RDONLY(inode))
            goto out_putf;
      err = -EPERM;
      if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
            goto out_putf;
      mutex_lock(&inode->i_mutex);
      if (mode == (mode_t) -1)
            mode = inode->i_mode;
      newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
      newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
      err = notify_change(dentry, &newattrs);
      mutex_unlock(&inode->i_mutex);

out_putf:
      fput(file);
out:
      return err;
}

asmlinkage long sys_fchmodat(int dfd, const char __user *filename,
                       mode_t mode)
{
      struct nameidata nd;
      struct inode * inode;
      int error;
      struct iattr newattrs;

      error = __user_walk_fd(dfd, filename, LOOKUP_FOLLOW, &nd);
      if (error)
            goto out;
      inode = nd.dentry->d_inode;

      error = -EROFS;
      if (IS_RDONLY(inode))
            goto dput_and_out;

      error = -EPERM;
      if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
            goto dput_and_out;

      mutex_lock(&inode->i_mutex);
      if (mode == (mode_t) -1)
            mode = inode->i_mode;
      newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
      newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
      error = notify_change(nd.dentry, &newattrs);
      mutex_unlock(&inode->i_mutex);

dput_and_out:
      path_release(&nd);
out:
      return error;
}

asmlinkage long sys_chmod(const char __user *filename, mode_t mode)
{
      return sys_fchmodat(AT_FDCWD, filename, mode);
}

static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
{
      struct inode * inode;
      int error;
      struct iattr newattrs;

      error = -ENOENT;
      if (!(inode = dentry->d_inode)) {
            printk(KERN_ERR "chown_common: NULL inode\n");
            goto out;
      }
      error = -EROFS;
      if (IS_RDONLY(inode))
            goto out;
      error = -EPERM;
      if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
            goto out;
      newattrs.ia_valid =  ATTR_CTIME;
      if (user != (uid_t) -1) {
            newattrs.ia_valid |= ATTR_UID;
            newattrs.ia_uid = user;
      }
      if (group != (gid_t) -1) {
            newattrs.ia_valid |= ATTR_GID;
            newattrs.ia_gid = group;
      }
      if (!S_ISDIR(inode->i_mode))
            newattrs.ia_valid |=
                  ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
      mutex_lock(&inode->i_mutex);
      error = notify_change(dentry, &newattrs);
      mutex_unlock(&inode->i_mutex);
out:
      return error;
}

asmlinkage long sys_chown(const char __user * filename, uid_t user, gid_t group)
{
      struct nameidata nd;
      int error;

      error = user_path_walk(filename, &nd);
      if (error)
            goto out;
      error = chown_common(nd.dentry, user, group);
      path_release(&nd);
out:
      return error;
}

asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user,
                       gid_t group, int flag)
{
      struct nameidata nd;
      int error = -EINVAL;
      int follow;

      if ((flag & ~AT_SYMLINK_NOFOLLOW) != 0)
            goto out;

      follow = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
      error = __user_walk_fd(dfd, filename, follow, &nd);
      if (error)
            goto out;
      error = chown_common(nd.dentry, user, group);
      path_release(&nd);
out:
      return error;
}

asmlinkage long sys_lchown(const char __user * filename, uid_t user, gid_t group)
{
      struct nameidata nd;
      int error;

      error = user_path_walk_link(filename, &nd);
      if (error)
            goto out;
      error = chown_common(nd.dentry, user, group);
      path_release(&nd);
out:
      return error;
}


asmlinkage long sys_fchown(unsigned int fd, uid_t user, gid_t group)
{
      struct file * file;
      int error = -EBADF;
      struct dentry * dentry;

      file = fget(fd);
      if (!file)
            goto out;

      dentry = file->f_path.dentry;
      audit_inode(NULL, dentry);
      error = chown_common(dentry, user, group);
      fput(file);
out:
      return error;
}

static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
                              int flags, struct file *f,
                              int (*open)(struct inode *, struct file *))
{
      struct inode *inode;
      int error;

      f->f_flags = flags;
      f->f_mode = ((flags+1) & O_ACCMODE) | FMODE_LSEEK |
                        FMODE_PREAD | FMODE_PWRITE;
      inode = dentry->d_inode;
      if (f->f_mode & FMODE_WRITE) {
            error = get_write_access(inode);
            if (error)
                  goto cleanup_file;
      }

      f->f_mapping = inode->i_mapping;
      f->f_path.dentry = dentry;
      f->f_path.mnt = mnt;
      f->f_pos = 0;
      f->f_op = fops_get(inode->i_fop);
      file_move(f, &inode->i_sb->s_files);

      error = security_dentry_open(f);
      if (error)
            goto cleanup_all;

      if (!open && f->f_op)
            open = f->f_op->open;
      if (open) {
            error = open(inode, f);
            if (error)
                  goto cleanup_all;
      }

      f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);

      file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);

      /* NB: we're sure to have correct a_ops only after f_op->open */
      if (f->f_flags & O_DIRECT) {
            if (!f->f_mapping->a_ops ||
                ((!f->f_mapping->a_ops->direct_IO) &&
                (!f->f_mapping->a_ops->get_xip_page))) {
                  fput(f);
                  f = ERR_PTR(-EINVAL);
            }
      }

      return f;

cleanup_all:
      fops_put(f->f_op);
      if (f->f_mode & FMODE_WRITE)
            put_write_access(inode);
      file_kill(f);
      f->f_path.dentry = NULL;
      f->f_path.mnt = NULL;
cleanup_file:
      put_filp(f);
      dput(dentry);
      mntput(mnt);
      return ERR_PTR(error);
}

/*
 * Note that while the flag value (low two bits) for sys_open means:
 *    00 - read-only
 *    01 - write-only
 *    10 - read-write
 *    11 - special
 * it is changed into
 *    00 - no permissions needed
 *    01 - read-permission
 *    10 - write-permission
 *    11 - read-write
 * for the internal routines (ie open_namei()/follow_link() etc). 00 is
 * used by symlinks.
 */
static struct file *do_filp_open(int dfd, const char *filename, int flags,
                         int mode)
{
      int namei_flags, error;
      struct nameidata nd;

      namei_flags = flags;
      if ((namei_flags+1) & O_ACCMODE)
            namei_flags++;

      error = open_namei(dfd, filename, namei_flags, mode, &nd);
      if (!error)
            return nameidata_to_filp(&nd, flags);

      return ERR_PTR(error);
}

struct file *filp_open(const char *filename, int flags, int mode)
{
      return do_filp_open(AT_FDCWD, filename, flags, mode);
}
EXPORT_SYMBOL(filp_open);

/**
 * lookup_instantiate_filp - instantiates the open intent filp
 * @nd: pointer to nameidata
 * @dentry: pointer to dentry
 * @open: open callback
 *
 * Helper for filesystems that want to use lookup open intents and pass back
 * a fully instantiated struct file to the caller.
 * This function is meant to be called from within a filesystem's
 * lookup method.
 * Beware of calling it for non-regular files! Those ->open methods might block
 * (e.g. in fifo_open), leaving you with parent locked (and in case of fifo,
 * leading to a deadlock, as nobody can open that fifo anymore, because
 * another process to open fifo will block on locked parent when doing lookup).
 * Note that in case of error, nd->intent.open.file is destroyed, but the
 * path information remains valid.
 * If the open callback is set to NULL, then the standard f_op->open()
 * filesystem callback is substituted.
 */
struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
            int (*open)(struct inode *, struct file *))
{
      if (IS_ERR(nd->intent.open.file))
            goto out;
      if (IS_ERR(dentry))
            goto out_err;
      nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->mnt),
                                   nd->intent.open.flags - 1,
                                   nd->intent.open.file,
                                   open);
out:
      return nd->intent.open.file;
out_err:
      release_open_intent(nd);
      nd->intent.open.file = (struct file *)dentry;
      goto out;
}
EXPORT_SYMBOL_GPL(lookup_instantiate_filp);

/**
 * nameidata_to_filp - convert a nameidata to an open filp.
 * @nd: pointer to nameidata
 * @flags: open flags
 *
 * Note that this function destroys the original nameidata
 */
struct file *nameidata_to_filp(struct nameidata *nd, int flags)
{
      struct file *filp;

      /* Pick up the filp from the open intent */
      filp = nd->intent.open.file;
      /* Has the filesystem initialised the file for us? */
      if (filp->f_path.dentry == NULL)
            filp = __dentry_open(nd->dentry, nd->mnt, flags, filp, NULL);
      else
            path_release(nd);
      return filp;
}

/*
 * dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an
 * error.
 */
struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
{
      int error;
      struct file *f;

      error = -ENFILE;
      f = get_empty_filp();
      if (f == NULL) {
            dput(dentry);
            mntput(mnt);
            return ERR_PTR(error);
      }

      return __dentry_open(dentry, mnt, flags, f, NULL);
}
EXPORT_SYMBOL(dentry_open);

/*
 * Find an empty file descriptor entry, and mark it busy.
 */
int get_unused_fd_flags(int flags)
{
      struct files_struct * files = current->files;
      int fd, error;
      struct fdtable *fdt;

      error = -EMFILE;
      spin_lock(&files->file_lock);

repeat:
      fdt = files_fdtable(files);
      fd = find_next_zero_bit(fdt->open_fds->fds_bits, fdt->max_fds,
                        files->next_fd);

      /*
       * N.B. For clone tasks sharing a files structure, this test
       * will limit the total number of files that can be opened.
       */
      if (fd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
            goto out;

      /* Do we need to expand the fd array or fd set?  */
      error = expand_files(files, fd);
      if (error < 0)
            goto out;

      if (error) {
            /*
             * If we needed to expand the fs array we
             * might have blocked - try again.
             */
            error = -EMFILE;
            goto repeat;
      }

      FD_SET(fd, fdt->open_fds);
      if (flags & O_CLOEXEC)
            FD_SET(fd, fdt->close_on_exec);
      else
            FD_CLR(fd, fdt->close_on_exec);
      files->next_fd = fd + 1;
#if 1
      /* Sanity check */
      if (fdt->fd[fd] != NULL) {
            printk(KERN_WARNING "get_unused_fd: slot %d not NULL!\n", fd);
            fdt->fd[fd] = NULL;
      }
#endif
      error = fd;

out:
      spin_unlock(&files->file_lock);
      return error;
}

int get_unused_fd(void)
{
      return get_unused_fd_flags(0);
}

EXPORT_SYMBOL(get_unused_fd);

static void __put_unused_fd(struct files_struct *files, unsigned int fd)
{
      struct fdtable *fdt = files_fdtable(files);
      __FD_CLR(fd, fdt->open_fds);
      if (fd < files->next_fd)
            files->next_fd = fd;
}

void fastcall put_unused_fd(unsigned int fd)
{
      struct files_struct *files = current->files;
      spin_lock(&files->file_lock);
      __put_unused_fd(files, fd);
      spin_unlock(&files->file_lock);
}

EXPORT_SYMBOL(put_unused_fd);

/*
 * Install a file pointer in the fd array.
 *
 * The VFS is full of places where we drop the files lock between
 * setting the open_fds bitmap and installing the file in the file
 * array.  At any such point, we are vulnerable to a dup2() race
 * installing a file in the array before us.  We need to detect this and
 * fput() the struct file we are about to overwrite in this case.
 *
 * It should never happen - if we allow dup2() do it, _really_ bad things
 * will follow.
 */

void fastcall fd_install(unsigned int fd, struct file * file)
{
      struct files_struct *files = current->files;
      struct fdtable *fdt;
      spin_lock(&files->file_lock);
      fdt = files_fdtable(files);
      BUG_ON(fdt->fd[fd] != NULL);
      rcu_assign_pointer(fdt->fd[fd], file);
      spin_unlock(&files->file_lock);
}

EXPORT_SYMBOL(fd_install);

long do_sys_open(int dfd, const char __user *filename, int flags, int mode)
{
      char *tmp = getname(filename);
      int fd = PTR_ERR(tmp);

      if (!IS_ERR(tmp)) {
            fd = get_unused_fd_flags(flags);
            if (fd >= 0) {
                  struct file *f = do_filp_open(dfd, tmp, flags, mode);
                  if (IS_ERR(f)) {
                        put_unused_fd(fd);
                        fd = PTR_ERR(f);
                  } else {
                        fsnotify_open(f->f_path.dentry);
                        fd_install(fd, f);
                  }
            }
            putname(tmp);
      }
      return fd;
}

asmlinkage long sys_open(const char __user *filename, int flags, int mode)
{
      long ret;

      if (force_o_largefile())
            flags |= O_LARGEFILE;

      ret = do_sys_open(AT_FDCWD, filename, flags, mode);
      /* avoid REGPARM breakage on x86: */
      prevent_tail_call(ret);
      return ret;
}
EXPORT_UNUSED_SYMBOL_GPL(sys_open); /* To be deleted for 2.6.25 */

asmlinkage long sys_openat(int dfd, const char __user *filename, int flags,
                     int mode)
{
      long ret;

      if (force_o_largefile())
            flags |= O_LARGEFILE;

      ret = do_sys_open(dfd, filename, flags, mode);
      /* avoid REGPARM breakage on x86: */
      prevent_tail_call(ret);
      return ret;
}

#ifndef __alpha__

/*
 * For backward compatibility?  Maybe this should be moved
 * into arch/i386 instead?
 */
asmlinkage long sys_creat(const char __user * pathname, int mode)
{
      return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
}

#endif

/*
 * "id" is the POSIX thread ID. We use the
 * files pointer for this..
 */
int filp_close(struct file *filp, fl_owner_t id)
{
      int retval = 0;

      if (!file_count(filp)) {
            printk(KERN_ERR "VFS: Close: file count is 0\n");
            return 0;
      }

      if (filp->f_op && filp->f_op->flush)
            retval = filp->f_op->flush(filp, id);

      dnotify_flush(filp, id);
      locks_remove_posix(filp, id);
      fput(filp);
      return retval;
}

EXPORT_SYMBOL(filp_close);

/*
 * Careful here! We test whether the file pointer is NULL before
 * releasing the fd. This ensures that one clone task can't release
 * an fd while another clone is opening it.
 */
asmlinkage long sys_close(unsigned int fd)
{
      struct file * filp;
      struct files_struct *files = current->files;
      struct fdtable *fdt;
      int retval;

      spin_lock(&files->file_lock);
      fdt = files_fdtable(files);
      if (fd >= fdt->max_fds)
            goto out_unlock;
      filp = fdt->fd[fd];
      if (!filp)
            goto out_unlock;
      rcu_assign_pointer(fdt->fd[fd], NULL);
      FD_CLR(fd, fdt->close_on_exec);
      __put_unused_fd(files, fd);
      spin_unlock(&files->file_lock);
      retval = filp_close(filp, files);

      /* can't restart close syscall because file table entry was cleared */
      if (unlikely(retval == -ERESTARTSYS ||
                 retval == -ERESTARTNOINTR ||
                 retval == -ERESTARTNOHAND ||
                 retval == -ERESTART_RESTARTBLOCK))
            retval = -EINTR;

      return retval;

out_unlock:
      spin_unlock(&files->file_lock);
      return -EBADF;
}

EXPORT_SYMBOL(sys_close);

/*
 * This routine simulates a hangup on the tty, to arrange that users
 * are given clean terminals at login time.
 */
asmlinkage long sys_vhangup(void)
{
      if (capable(CAP_SYS_TTY_CONFIG)) {
            /* XXX: this needs locking */
            tty_vhangup(current->signal->tty);
            return 0;
      }
      return -EPERM;
}

/*
 * Called when an inode is about to be open.
 * We use this to disallow opening large files on 32bit systems if
 * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
 * on this flag in sys_open.
 */
int generic_file_open(struct inode * inode, struct file * filp)
{
      if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
            return -EOVERFLOW;
      return 0;
}

EXPORT_SYMBOL(generic_file_open);

/*
 * This is used by subsystems that don't want seekable
 * file descriptors
 */
int nonseekable_open(struct inode *inode, struct file *filp)
{
      filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
      return 0;
}

EXPORT_SYMBOL(nonseekable_open);

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